Zoom objective, especially for a projector

ABSTRACT

A zoom objective with a varifocal ratio close to 2:1, particularly for a projector, has a stationary positive front component, a single axially shiftable negative lens and a stationary multilens rear component. An object-side positive lens member of the rear component, adjoining the shiftable negative lens, has a focal length smaller than that of the group constituted by the remaining, image-side lens members of this component. The negatively refracting third member of the rear component may be a doublet with a positively refracting cemented surface, convex toward the image side, or an equivalent lens pair separated by a small air gap.

FIELD OF THE INVENTION

My present invention relates to an optical system of the pancratic type,more often referred to as a varifocal or zoom objective, and inparticular to a projection objective of variable magnification ratio.

BACKGROUND OF THE INVENTION

It is known, e.g. from Austrian Pat. No. 290,162 and German utilitymodel No. 1,814,231, to design such objectives with two stationarycomponents and one movable component, i.e. an axially fixed positivelyrefracting front component, an axially shiftable negatively refractingintermediate component and an axially fixed positively refracting rearcomponent or basic objective. These prior-art constructions, with theshiftable component represented by a single biconcave lens, have yieldedvarifocal ratios of not more than about 1.7:1.

OBJECTS OF THE INVENTION

An object of my present invention is to provide an improved zoomobjective of this character whose varifocal ratio approaches the valueof 2:1.

A related object is to achieve this increased varifocal ratio in animproved optical system corrected for residual off-axial aberrations andother distortions over the entire image area, throughout the varifocalrange, with a relative aperture of preferably not less than 1:1.3.

SUMMARY OF THE INVENTION

I realize these aims, in accordance with my present invention, byconstituting the positive rear component as a combination of a firstpositive lens on the object side and a positively refracting multilensgroup on the image side including a second positive lens, a thirdpositive lens and a negative lens member therebetween, this componentdiffering from conventional four-lens basic objectives by the fact thatthe individual focal length of the first positive lens is smaller thanthat of the associated multilens group.

Such a dimensioning results in an increased power of the first positivelens which collects the light rays diverging behind the shiftablecomponent in such a manner that these rays impinge relatively close tothe axis upon the subsequent lenses. Thus, the power of the negativelens member of the multilens group can be considerably lower than inconventional objectives of similar relative aperture, with resultantflattening of astigmatic image curvature.

BRIEF DESCRIPTION OF THE DRAWING

The above and other features of my invention will now be described indetail with reference to the accompanying drawing in which:

FIGS. 1, 2 and 3 show a varifocal objective according to the inventionin three different positions;

FIG. 4 is a view similar to FIG. 2, showing another embodiment;

FIG. 4A is a view like FIG. 4 but illustrating a modification; and

FIG. 5 is another view similar to FIG. 2, representing a furtherembodiment.

SPECIFIC DESCRIPTION

The varifocal or zoom objective shown in FIGS. 1-3 comprises a positivefront component G_(I) in the shape of a nearly planoconvex positivemeniscus L₁, a negative intermediate component G_(II) represented by abiconcave lens L₂, and a rear component G_(III) consisting of a firstpositive lens L₃ followed by a multilens group R which is composed of asecond positive a second positive lens L₄, a negative lens L₅, a furtherpositive lens L₆ and a weakly refractive negative lens L₇.

Front lens L₁, which is considered stationary except for a possibleaxial adjustability for focusing purposes, has radii r₁, r₂ and an axialthickness d₁. Lens L₂, which is separated from lenses L₁ and L₃ by twovariable air spaces s₁ and s₂, has radii r₃, r₄ and a thickness d₂.Lenses L₃ and L₆ are biconvex, lenses L₄ and L₇ are positive andnegative menisci, respectively and lens L₅ is biconcave; their radii,thicknesses and separations have been designated r₅ -r₁₄, d₃ -d₇ and s₃-s₆. The system has an image plane IP which remains substantially fixedthroughout the axial displacement of component G_(II) between a positionof minimum focal length f_(min) (FIG. 1), a position of intermediatefocal length f_(med) (FIG. 2) and a position of maximum focal lengthf_(max) (FIG. 3).

According to an important feature of my invention, the first lens L₃ ofrear component G_(III) has an individual focal length f₃ which issmaller than the focal length f_(R) of the lens group R constituting theremainder of this component. This will become apparent from therepresentative numerical values given hereinafter for severalembodiments.

The final image-side lens L₇, which is only weakly refractive, serves ina manner known per se for a supplemental flattening of the image but maybe omitted if desired. An additional flattening effect can also berealized, as illustrated in FIG. 4, by replacing the biconcave singletL₅ of FIGS. 1-3 with a doublet consisting of two lenses L₅ ', L₅ "cemented together along a surface of radius r₉₁₀ which is positivelyrefracting and convex toward the image side, the refractive index oflens L₅ ' being greater than that of lens L₅ ". The collective effect ofthis cemented surface allows a reduction in the other positive lenses ofthe basic objective G_(III) and yields a Petzval surface whose radius isa multiple of the minimum overall focal length f_(min).

As shown in FIG. 4A, the lenses L₅ ' and L₅ " of axial thickness d₅ ',d₅ " may be separated by a small air gap of width s₉₁₀ between surfacesof identical radii of curvature r₉₁₀ ' and r₉₁₀ ".

The system of FIG. 4 or FIG. 4A could also be supplemented by aflattening lens L₇ as shown in FIGS. 1-3.

The front component G_(I) in any of the aforedescribed systems may alsobe split into two lenses which are either cemented together or separatedby a small air gap. The latter arrangement has been illustrated in FIG.5 where a negative meniscus L₁ ' and a nearly planoconvex lens L₁ " areclosely juxtaposed with confronting surfaces of identical radii r₀ ' andr₀ ", the width of the gap having been designated s₀.

The front component G_(I), or at least one of its constituents such asthe second lens L₁ " of FIG. 5, may have a referactive index low enough(i.e. of about 1.5) to allow its manufacture from synthetic resin ratherthan glass, e.g. a polyacrylate known as Plexiglass N7. This entails aconsiderable saving in cost, on account of the large diameter of thatlens member.

In the following Tables A to F I have listed representative numericalvalues for the radii of curvature, axial thicknesses and separations forthe several lenses of each of the embodiments shown in the drawing,based upon a value of unity for the focal length f_(min) in allinstances (without lens L₇). The Tables also include the refractiveindices n_(d) and the Abbe numbers ν_(d) of these lenses, as well as theindividual focal lengths f₃ of lens L₃ and f_(R) of lens group R.

                  TABLE A                                                         ______________________________________                                        (FIGS. 1 - 3)                                                                                   n.sub.d                                                                             ν.sub.d                                            ______________________________________                                        r.sub.1 = +3.366                                                              L.sub.1     d.sub.1 = 0.190                                                                           1.504  66.9                                           r.sub.2 = +25.552                                                                         0.133 f.sub.min                                                               s.sub.1 =                                                                     1.967 f.sub.max                                                   r.sub.3 = -10.498                                                             L.sub.2     d.sub.2 = 0.089                                                                           1.651  55.9                                           r.sub.4 = +2.393                                                                          2.182 f.sub.min                                                               s.sub.2 =                                                                     0.348 f.sub.max                                                   r.sub.5 = 30 1.445                                                            L.sub.3     d.sub.3 = 0.215                                                                           1.603  60.6 f.sub.3 = +1.831                          r.sub.6 = -4.427                                                                          s.sub.3 = 0.006                                                   r.sub.7 = +0.712                                                              L.sub.4     d.sub.4 = 0.307                                                                           1.603  60.6                                           r.sub. 8 = +3.565                                                                         s.sub.4 = 0.114                                                   r.sub.9 = -5.063                                                              L.sub.5     d.sub.5 = 0.393                                                                           1.847  23.8 f.sub.R = +1.971                          r.sub.10 = +0.396                                                                         s.sub.5 = 0.185                                                   r.sub.11 = +0.689                                                             L.sub.6     d.sub.6 = 0.209                                                                           1.784  43.9                                           r.sub.12 = -1.505                                                                         f.sub.min = 1.000                                                             f.sub.max = 1.823                                                 relative aperture                                                                         1 : 1.3                                                           image diagonal                                                                            0.424                                                             ______________________________________                                    

                  TABLE B                                                         ______________________________________                                        (FIGS. 1 - 3)                                                                                   n.sub.d                                                                            ν.sub.d                                             ______________________________________                                        r.sub.1 = +3.240                                                              L.sub.1     d.sub.1 = 0.193                                                                           1.504  66.9                                           r.sub.2 = +18.049                                                                         0.135 f.sub.min                                                               s.sub.1 =                                                                     2.001 f.sub.r.sub.-r.sub.3  = -12.185                             L.sub.2     d.sub.2 = 0.090                                                                           1.651  55.9                                           r.sub.4 = +2.366                                                                          2.220 f.sub.min                                                               s.sub.2 =                                                                     0.354 f.sub.max                                                   r.sub.5 = +1.388                                                              L.sub.3     d.sub.3 = 0.219                                                                           1.603  60.6 f.sub.3 = +1.922                          r.sub.6 = -6.610                                                                          s.sub.3 = 0.006                                                   r.sub.7 = +0.762                                                              L.sub.4     d.sub.4 = 0.312                                                                           1.641  60.1                                            r.sub.8 = +3.662                                                                         s.sub.4 = 0.116                                                   r.sub.9 = -4.999                                                              L.sub.5     d.sub.5 = 0.380                                                                           1.805  25.4 f.sub.R = +1.982                          r.sub.10 = +0.413                                                                         s.sub.5 = 0.180                                                   r.sub.11 = +0.724                                                             L.sub.6     d.sub.6 = 0.193                                                                           1.788  47.4                                           r.sub.12 = -1.670                                                                         f.sub.min = 1.000                                                             f.sub.max = 1.824                                                 relative aperture                                                                         1 : 1.3                                                           image diagonal                                                                            0.431                                                             ______________________________________                                    

Following are the additional parameters for an expanded system of thistype including the lens L₇.

                  TABLE B'                                                        ______________________________________                                                             n.sub.d                                                                            ν.sub.d                                          ______________________________________                                        r.sub.13 = +1.094                                                                          s.sub.6 = 0.006                                                  L.sub.7      d.sub.7 = 0.148                                                                             1.603  60.6                                        r.sub.14 = +0.826                                                                          f.sub.min = 0.992                                                             f.sub.max = 1.813                                                relative aperture                                                                          1: 1.3                                                           image diagonal                                                                             0.431                                                            ______________________________________                                    

The relative aperture and the image diagonal remain unchanged by theinclusion of this additional lens.

The lens L₁ of Table A can readily be replaced by one of still lowerrefractive index manufactured, if desired, from transparent plastic asdiscussed above. Such a lens would have the following parameters:

                  TABLE A'                                                        ______________________________________                                                              n.sub.d                                                                            ν.sub.d                                         ______________________________________                                        r.sub.1 = +3.366                                                              L.sub.1       d.sub.1 = 0.190                                                                             1.501  56.4                                       r.sub.2 = +25.552                                                                           f.sub. min = 0.997                                                            f.sub. max = 1.820                                              ______________________________________                                    

This modified objective has the same relative aperture and imagediagonal as that of Table A.

                  TABLE C                                                         ______________________________________                                        (FIGS. 1-3)                                                                                     n.sub.d                                                                            ν.sub.d                                             ______________________________________                                        r.sub.1 = +3.471                                                              L.sub.1     d.sub.1 = 0.190                                                                           1.504  66.9                                           r.sub.2 = +33.682                                                                         0.133 f.sub.min                                                               s.sub.1 =                                                                     1.967 f.sub.max                                                   r.sub.3 = -11.967                                                             L.sub.2     d.sub.2 = 0.088                                                                           1.651  55.9                                           r.sub.4 = +2.324                                                                          2.180 f.sub.min                                                               s.sub.2 =                                                                     0.348 f.sub.max                                                   r.sub.5 = +1.444                                                              L.sub.3     d.sub.3 = 0.215                                                                           1.603  60.6 f.sub.3 = +1.830                          r.sub.6 = -4.425                                                                          s.sub.3 = 0.006                                                   r.sub.7 = +0.711                                                              L.sub.4     d.sub.4 = 0.307                                                                           1.603  60.6                                           r.sub.8 = +3.563                                                                          s.sub.4 = 0.114                                                    r.sub.9 = -4,910                                                             L.sub.5     d.sub.5 = 0.373                                                                           1.805  25.4 f.sub.R = +2.002                          r.sub.10 = +0.394                                                                         s.sub.5 = 0.190                                                   r.sub.11 = +0.696                                                             L.sub.6     d.sub.6 = 0.209                                                                           1.744  44.8                                           r.sub.12 = -1.444                                                                         f.sub.min = 1.000                                                             f.sub.max = 1.824                                                 relative aperture                                                                         1 : 1.3                                                           image diagonal                                                                            0.423                                                             ______________________________________                                    

                  TABLE C'                                                        ______________________________________                                                              n.sub.d                                                                            ν.sub.d                                         ______________________________________                                                      s.sub.6 = 0.006                                                 r.sub.13 = +1.074                                                             L.sub.7       d.sub.7 = 0.126                                                                             1.603  60.6                                       r.sub.14 = +0.920                                                                           f.sub.min = 0.974                                                             f.sub.max = 1.779                                               relative aperture                                                                           1 : 1.3                                                         image diagonal                                                                              0.423                                                           ______________________________________                                    

                  TABLE D                                                         ______________________________________                                        (FIG. 4)                                                                                        n.sub.d                                                                            ν.sub.d                                             ______________________________________                                        r.sub.1 = +3.249                                                              L.sub.1     d.sub.1 = 0.194                                                                           1.504   66.9                                          r.sub.2 = +18.098                                                                         0.136 f.sub.min                                                               s.sub.1 =                                                                     2.007 f.sub.max                                                   r.sub.3 = -9.679                                                              L.sub.2     d.sub.2 = 0.090                                                                           1.652   44.9                                          r.sub.4 = +2.501                                                                          2.226 f.sub.min                                                               s.sub.2 =                                                                     0.355 f.sub.max                                                   r.sub.5 = +1.392                                                              L.sub.3     d.sub.3 = 0.219                                                                           1.603   60.6                                                                              f.sub.3 = +1.927                          r.sub.6 = -6.628                                                                          s.sub.3 = 0.006                                                   r.sub.7 = +0.775                                                              L.sub.4     d.sub.4 = 0.313                                                                           1.641   60.1                                          r.sub.8 = +3.993                                                                          s.sub.4 = 0.116                                                   r.sub.9  = -3.249                                                             L.sub.5 '   d.sub.5 =0.316                                                                            1.805   25.4                                           r.sub.910 '=-0.522                                                           L.sub.5 "   d.sub.6 =0.064                                                                            1.762   26.5                                                                              f.sub.R = +2.022                          r.sub.10 = +0.411                                                                         s.sub.5 =0.181                                                    r.sub.11 = +0.685                                                             L.sub.6     d.sub.6 =0.194                                                                            1.788   47.4                                          r.sub.12 =-2.267                                                                          f.sub.min = 1.000                                                             f.sub.max = 1.826                                                 relative aperture                                                                         1 : 1.3                                                           image diagonal                                                                            0.432                                                             ______________________________________                                    

                  TABLE E                                                         ______________________________________                                        (FIG. 4A)                                                                                       n.sub.d                                                                            ν.sub.d                                             ______________________________________                                        r.sub.1 = +3.744                                                              L.sub.1     d.sub.1 = 0.191                                                                           1.504  66.9                                           r.sub.2 = +66.833                                                                         0.136 f.sub.min                                                               s.sub.1 =                                                                     2.009 f.sub.max                                                   r.sub.3 = -6.041                                                              L.sub.2     d.sub.2 = 0.090                                                                           1.651  55.9                                           r.sub.4 = +2.966                                                                          2.229 f.sub.min                                                               s.sub.2 =                                                                     0.355 f.sub.max                                                   r.sub.5 = +1.393                                                              L.sub.3     d.sub.3 = 0.220                                                                           1.603  60.6 f.sub.3 =+1.929                           r.sub.6 = -6.636                                                                          s.sub.3 = 0.006                                                   r.sub.7 = +0.765                                                              L.sub.4     d.sub.4 = 0.313                                                                           1.641  60.1                                           r.sub.8 = +4.015                                                                          s.sub.4 = 0.116                                                   r.sub.9  = -3.253                                                             L.sub.5 '   d.sub.5 = 0.317                                                                           1.805  25.4                                           r.sub.910 '= -1.012                                                                       s.sub.910 = 0.006       f.sub.R =+2.098                           r.sub.910 "=-1.012                                                            L.sub.5 "   d.sub.6 =0.064                                                                            1.762  26.5                                           r.sub.10 = +0.415                                                                         s.sub.5 = 0.181                                                   r.sub.11 = +0.675                                                             L.sub.6     d.sub.6 = 0.194                                                                           1.788  47.4                                           r.sub.12 = -2.559                                                                         f.sub.min = 1.000                                                             f.sub.max = 1.826                                                 relative aperture                                                                         1 : 1.3                                                           image diagonal                                                                            0.433                                                             ______________________________________                                    

                  TABLE F                                                         ______________________________________                                        (FIG. 5)                                                                                        n.sub.d                                                                            ν.sub.d                                             ______________________________________                                        r.sub.1 = +3.314                                                              L.sub.1 "   d.sub.1 '= 0.096                                                                          1.689  31.2                                           r.sub.0 ' = +2.103                                                                        s.sub.0 = 0.032                                                   r.sub.0 " = +2.103                                                            L.sub.1 "   d.sub.1 " = 0.225                                                                         1.501  56.4                                           r.sub.2 = -40.814                                                                         0.124 f.sub.min                                                               s.sub.1 =                                                                     1.989 f.sub.max                                                   r.sub.3 = -12.671                                                             L.sub.2     d.sub.2 = 0.090                                                                           1.651  55.9                                           r.sub.4 = +2.348                                                                          2.219 f.sub.min                                                               s.sub.2 =                                                                     0.354 f.sub.max                                                   r.sub.5 = +1.387                                                              L.sub.3     d.sub.3 = 219                                                                             1.603  60.6 f.sub.4 = +1.921                          r.sub.6 = -6.608                                                                          s.sub.3  = 0.006                                                  r.sub.7 = +756                                                                L.sub.4     d.sub.4 = 0.312                                                                           1.641  60.1                                           r.sub.8 = +3.491                                                                          s.sub.4 = 0.116                                                   r.sub.9 = -4.998                                                              L.sub.5     d.sub.5 = 0.380                                                                           1.805  25.4 f.sub.R = +1.968                          r.sub.10 = +0.405                                                                         s.sub.5 = 0.167                                                   r.sub.11 = +0.714                                                             L.sub.6     d.sub.6 = 0.193                                                                           1.788  47.4                                           r.sub.12 = -1.566                                                                         f.sub.min = 1.000                                                             f.sub.max = 1.831                                                 relative aperture                                                                         1 : 1.3                                                           image diagonal                                                                            0.431                                                             ______________________________________                                    

From the foregoing values it will be noted that the focal length f₃ oflens L₃ is not only less than the focal length f_(R) of the associatedgroup R (with or without the additional flattening lens L₇) but alsoless than the absolute values of the individual focal lengths of thepreceding components G_(I) and G_(II).

I claim:
 1. A varifocal objective consisting of an axially fixedpositively refracting front component, an axially shiftable negativelyrefracting intermediate component, and an axially fixed positivelyrefracting rear component constituted by an object-side first positivelens and an image-side positively refracting multilens group; saidmultilens group comprising a second positive lens, a third positivelens, and a negative lens between said second and third positive lenses;said front component L₁, said intermediate component L₂, said firstpositive lens L₃, said second positive lens L₄, said negative lens L₅and said third positive lens L₆ having radii of curvature r₁ -r₁₂, axialthicknesses d₁ -d₆, separations s₁ -s₅, refractive indices n_(d) andAbbe numbers ν_(d) substantially as given in the following table:

    ______________________________________                                                                 n.sub.d                                                                            ν.sub.d                                      ______________________________________                                                   r.sub.1 =                                                                             +3.24                                                      L.sub.1                   d.sub.1 =                                                                              0.19    1.50 67                                       r.sub.2 =                                                                             +18.05                                                                                        0.14 f.sub.min                                                       s.sub.1 =                                                                              2.00 f.sub.max                                        r.sub.3 =                                                                             -12.19                                                     L.sub.2                   d.sub.2 =                                                                              0.09    1.65 56                                       r.sub.4 =                                                                             +2.37                                                                                         2.22 f.sub.min                                                       s.sub.2 =                                                                              0.35 f.sub.max                                        r.sub.5 =                                                                             +1.39                                                      L.sub.3                   d.sub.3 =                                                                              0.22    1.60 61                                       r.sub.6 =                                                                             -6.61                                                                                s.sub.3 =                                                                              0.01                                                  r.sub.7 =                                                                             +0.76                                                      L.sub.4                   d.sub.4 =                                                                              0.31    1.64 60                                       r.sub.8 =                                                                             +3.66                                                                                s.sub.4 =                                                                              0.12                                                  r.sub.9 =                                                                             -5.00                                                      L.sub.5                   d.sub.5 =                                                                              0.38    1.81 25                                       r.sub.10 =                                                                            +0.41                                                                                s.sub.5 =                                                                              0.18                                                  r.sub.11 =                                                                            +0.72                                                      L.sub.6                   d.sub.6 =                                                                              0.19    1.79 47                                       r.sub.12 =                                                                            -1.67                                                      ______________________________________                                    


2. A varifocal objective consisting of an axially fixed positivelyrefracting front component, an axially shiftable negatively refractingintermediate component, and an axially fixed positively refracting rearcomponent constituted by an object-side first positive lens and animage-side positively refracting multilens group; said multilens groupcomprising a second positive lens, a third positive lens, and a negativelens between said second and third positive lenses; said front componentL₁, said intermediate component L₂, said first positive lens L₃, saidsecond positive lens L₄, said negative lens L₅ and said third positivelens L₆ having radii of curvature r₁ -r₁₂, axial thicknesses d₁ -d₆,separations s₁ -s₅, refractive indices n_(d) and Abbe numbers ν_(d)substantially as given in the following table:

    ______________________________________                                                               n.sub.d                                                                            ν.sub.d                                        ______________________________________                                        r.sub.1 = +3.37                                                               L.sub.1        d.sub.1 = 0.19                                                                              1.50   67                                        r.sub.2 = +25.55                                                                             0.13 f.sub.min                                                                s.sub.1 =                                                                     1.97 f.sub.max                                                 r.sub.3 = -10.50                                                              L.sub.2        d.sub.2 = 0.09                                                                              1.65   56                                        r.sub.4 = +2.40                                                                              2.18 f.sub.min                                                                s.sub.2 =                                                                     0.35 f.sub.max                                                  r.sub.5 = +1.45                                                              L.sub.3        d.sub.3 = 0.22                                                                              1.60   61                                        r.sub.6 = -4.43                                                                              s.sub.3 = 0.01                                                 r.sub.7 = +0.71                                                               L.sub.4        d.sub.4 = 0.31                                                                              1.60   61                                        r.sub.8 = +3.57                                                                              s.sub.4 = 0.11                                                 r.sub.9 = -5.06                                                               L.sub.5        d.sub.5  = 0.39                                                                             1.85   24                                        r.sub.10 = +0.40                                                                             s.sub.5 l = 0.190                                              r.sub.11 = +0.69                                                              L.sub.6        d.sub.6 = 0.21                                                                              1.78   44                                        r.sub.12 = -1.51                                                              ______________________________________                                    


3. A varifocal objective consisting of an axially fixed positivelyrefracting front component, an axially shiftable negatively refractingintermediate component, and an axially fixed positively refracting rearcomponent constituted by an object-side first positive lens and animage-side positively refracting multilens group; said multilens groupcomprising a second positive lens, a third positive lens, and a negativelens between said second and third positive lenses; said front componentL₁, said intermediate component L₂, said first positive lens L₃, saidsecond positive lens L₄, said negative lens L₅ and said third positivelens L₆ having radii of curvature r₁ -r₁₂, axial thicknesses d₁ -d₆,separations s₁ -s₅, refractive indices n_(d) and Abbe numbers ν_(d)substantially as given in the following table:

    ______________________________________                                                               n.sub.d                                                                            ν.sub.d                                        ______________________________________                                        r.sub.1 = +3.37                                                               L.sub.1        d.sub.1 = 0.19                                                                              1.50   56                                        r.sub.2 =+25.55                                                                              0.13 f.sub.min                                                                s.sub.1 =                                                                     1.97 f.sub.max                                                 r.sub.3 = -10.50                                                              L.sub.2        d.sub.2 = 0.09                                                                              1.65   56                                        r.sub.4 = +2.40                                                                              2.18 f.sub.min                                                                s.sub.2 =                                                                     0.35 f.sub.max                                                 r.sub.5 = +1.45                                                               L.sub.3        d.sub.3 = 0.21                                                                              1.60   61                                        r.sub.6 = -4.43                                                                              s.sub.3 = 0.01                                                  r.sub.7 = +0.71                                                              L.sub.4        d.sub.4 = 0.31                                                                              1.60   61                                        r.sub.8 = +3.57                                                                              s.sub.4 = 0.11                                                  r.sub.9 = -5.06                                                              L.sub.5        d.sub.5 = 0.39                                                                              1.85   24                                        r.sub.10 = +0.40                                                                             s.sub.5 = 0.19                                                 r.sub.11 = +0.69                                                              L.sub.6        d.sub.6 = 0.21                                                                              1.78   44                                        r.sub.12 = -1.51                                                              ______________________________________                                    


4. A varifocal objective as defined in claim 3 wherein said multlensgroup further comprises a further negative lens L₇ separated from saidthird positive lens L₆ by an air space s₆ and having radii r₁₃, r₁₄, anaxial thickness d₇, a refractive index n_(d) and an Abbe number ν_(d)substantially as given in the following table:

    ______________________________________                                                           n.sub.d ν.sub.d                                         ______________________________________                                                     s.sub.6 = 0.01                                                   r.sub.13 = +1.10                                                              L.sub.7      d.sub.7 = 0.15                                                                            1.60      61                                         r.sub.14 = +0.83                                                              ______________________________________                                    


5. A varifocal objective consisting of an axially fixed positivelyrefracting front component, an axially shiftable negatively refractingintermediate component, and an axially fixed positively refracting rearcomponent constituted by an object-side first positive lens and animage-side positively refracting multilens group; said multilens groupcomprising a second positive lens, a third positive lens, and a negativelens between said second and third positive lenses; said front componentL₁, said intermediate component L₂, said first positive lens L₃, saidsecond positive lens L₄, said negative lens L₅ and said third positivelens L₆ having radii of curvature r₁ -r₁₂, axial thicknesses d₁ -d₆,separations s₁ -s₅, refractive indices n_(d) and Abbe numbers ν_(d)substantially as given in the following table:

    ______________________________________                                                               n.sub.d                                                                            ν.sub.d                                        ______________________________________                                        r.sub.1 = +3.47                                                               L.sub. 1       d.sub.1 = 0.19                                                                              1.50   67                                        r.sub.2 = +33.68                                                                             0.13 f.sub.min                                                                s.sub.1 =                                                                     1.97 f.sub.max                                                  r.sub.3 = -11.97                                                             L.sub.2        d.sub.2 = 0.09                                                                              1.65   56                                        r.sub.4 = +2.32                                                                              2.18 f.sub.min                                                                s.sub.2 =                                                                     0.35 f.sub.max                                                 r.sub.5 = +1.44                                                               L.sub.3        d.sub.3 = 0.22                                                 r.sub.6 = -4.43                                                                              s.sub.3 = 0.01                                                 r.sub.7 = +0.71                                                               L.sub.4        d.sub.4 = 0.31                                                                              1.60   61                                        r.sub.8 =+3.56                                                                               s.sub.4 = 0.11                                                 r.sub.9 = -4.91                                                               L.sub.5        d.sub.5 = 0.37                                                                              1.81   25                                        r.sub.10 =  +0.39                                                                            s.sub.5 = 0.19                                                 r.sub.11 = +0.70                                                              L.sub.6        d.sub.6 = 0.21                                                                              1.74   45                                        r.sub.12 = -1.44                                                              ______________________________________                                    


6. A varifocal objective as defined in claim 5 wherein said multilensgroup further comprises a further negative lens L₇ separated from saidthird positive lens L₆ by an air space s₆ and having radii r₁₃, r₁₄, anaxial thickness d₇, a refractive index n_(d) and an Abbe number ν_(d)substantially as given in the following table:

    ______________________________________                                                           n.sub.d ν.sub.d                                         ______________________________________                                                     s.sub.6 = 0.01                                                   r.sub.13 = +1.07                                                              L.sub.7      d.sub.7 = 0.13                                                                            1.60      61                                         r.sub.14 = +0.92                                                              ______________________________________                                    


7. A varifocal objective consisting of an axially fixed positivelyrefracting front component consisting of two singlets, an axiallyshiftable negatively refracting intermediate component, and an axiallyfixed positively refracting rear component constituted by an object-sidefirst positive lens and an image-side positively refracting multilensgroup; said multilens group comprising a second positive lens, a thirdpositive lens, and a negative lens between said second and thirdpositive lenses; the singlets L₁ ', L₁ " of said front component, saidintermediate component L₂, said first positive lens L₃, said secondpositive lens L₄, said negative L₅ and said third positive lens L₆having radii of curvature r₁, r₀ ', r₀ ", r₂, r₃ -r₁₂, axial thicknessesd₁ ', d₁ ", d₂ -d₆, separations s₀ -s₅, refractive indices n_(d) andAbbe numbers ν_(d) substantially as given in the following table:

    ______________________________________                                                               n.sub.d                                                                            ν.sub.d                                        ______________________________________                                        r.sub.1 = +3.31                                                               L.sub.1 '      d.sub.1 ' = 0.10                                                                            1.69   31                                        r.sub.0 '= +2.10                                                                             s.sub.0 = 0.03                                                 r.sub.0 "= +2.10                                                              L.sub.1 "      d.sub.1 " = 0.23                                                                            1.50   56                                        r.sub.2 = -40.81                                                                             0.12 f.sub.min                                                                s.sub.1 =                                                                     1.99 f.sub.max                                                 r.sub.3 = -12.67                                                              L.sub.2        d.sub.2 = 0.09                                                                              1.65   56                                        r.sub.4 = +2.35                                                                              2.22 f.sub.min                                                                s.sub.2 =                                                                     0.35 f.sub.max                                                 r.sub.5 = +1.39                                                               L.sub.2        d.sub.3 = 0.22                                                                              1.60   61                                        r.sub.6 = -6.61                                                                              s.sub.3 = 0.01                                                 r.sub.7 = +0.76                                                               L.sub.4        d.sub.4 = 0.31                                                                              1.64   60                                        r.sub.8 = +3.49                                                                              s.sub.4 = 0.12                                                 r.sub.9 = -5.00                                                               L.sub.5        d.sub.5 = 0.38                                                                              1.81   25                                        r.sub.10 = -0.41                                                                             s.sub.5 = 0.17                                                 r.sub.11 = +0.71                                                              L.sub.6        d.sub.6 = 0.19                                                                              1.79   47                                        r.sub.12 = -1.57                                                              ______________________________________                                    


8. A varifocal objective consisting of an axially fixed positivelyrefracting front component, an axially shiftable negatively refractingintermediate component, and an axially fixed positively refracting rearcomponent constituted by an object-side first positive lens and animage-side positively refracting multilens group; said multilens groupcomprising a second positive lens, a third positive lens, and a negativelens member consisting of two cemented lenses between said second andthird positive lenses; said front component L₁, said intermediatecomponent L₂, said first positive lens L₃, said second positive lens L₄,said cemented lenses L₅ ', L₅ " and said third positive lens havingradii of curvature r₁ -r₉, r₉₁₀, r₁₀ -r₁₂, axial thicknesses d₁ -d₄, d₅', d₅ ", d₆, separations s₁ -s₅, refractive indices n_(d) and Abbenumbers ν_(d) substantially as given in the following table:

    ______________________________________                                                               n.sub.d                                                                            ν.sub.d                                        ______________________________________                                        r.sub.1 = +3.25                                                               L.sub.1        d.sub.1 = 0.19                                                                              1.50   67                                        r.sub.2 = +18.10                                                                             0.14 f.sub.min                                                                s.sub.1 =                                                                      2.01 f.sub.max                                                 r.sub.3 = -9.68                                                              L.sub.2        d.sub.2 = 0.09                                                                              1.65   45                                         r.sub.4 = +2.50                                                                             2.23 f.sub.min                                                                s.sub.2 =                                                                     0.36 f.sub.max                                                 r.sub.5 = +1.39                                                               L.sub.3        d.sub.3 = 0.22                                                                              1.60   61                                        r.sub.6 =-6.63                                                                               s.sub.3 = 0.01                                                  r.sub.7 = +0.78                                                              L.sub.4        d.sub.4  = 0.31                                                                             1.64   60                                        r.sub.8 = +3.99                                                                              s.sub.4 = 0.12                                                 r.sub.9 = -3.25                                                               L.sub.5 '      d.sub.5 ' = 0.32                                                                            1.81   25                                         r.sub.910 =-0.52                                                             L.sub.5 "      d.sub.5 "= 0.06                                                                             1.76   27                                        r.sub.10: = +0.41                                                                            s.sub.5 = 0.18                                                 r.sub.11 = +0.69                                                              L.sub.6        d.sub.6 = 0.19                                                                              1.79   47                                        r.sub.12 = -2.27                                                              ______________________________________                                    


9. A varifocal objective consisting of an axially fixed positivelyrefracting front component, an axially shiftable negatively refractingintermediate component, and an axially fixed positively refracting rearcomponent constituted by an object-side first positive lens and animage-side positively refracting multilens group; said multilens groupcomprising a second positive lens, a third positive lens and a negativelens member consisting of two closely juxtaposed lenses between saidsecond and third positive lenses; said front component L₁, saidintermediate component L₂, said first positive lens L₃, said secondpositive lens L₄, said juxtaposed lenses L₅ ', L₅ " and said thirdpositive lens having radii of curvature r₁ -r₉, r₉₁₀ ', r₉₁₀ ", r₁₀-r₁₂, axial thicknesses d₁ -d₄, d₅ 'd₅ ", d₆, separations s₁ -s₄, s₉₁₀,s₁₁, refractive indices n_(d) and Abbe numbers ν_(d) substantially asgiven in the following table:

    ______________________________________                                                               n.sub.d                                                                            ν.sub.d                                        ______________________________________                                        r.sub.1 = +3.74                                                               L.sub.1        d.sub.1 = 0.19                                                                              1.50   67                                        r.sub.2 = +66.83                                                                             0.14 f.sub.min                                                                s.sub.1 =                                                                     2.01 f.sub.max                                                  r.sub.3 = -6.04                                                              L.sub.2        d.sub.2 = 0.09                                                                              1.65   56                                         r.sub.4 = +2.97                                                                             2.23 f.sub.min                                                                s.sub.2 =                                                                     0.36 f.sub.max                                                 r.sub.5 = +1.39                                                               L.sub.3        d.sub.3 = 0.22                                                                              1.60   61                                        r.sub.6 = -6.64                                                                              s.sub.3 = 0.01                                                 r.sub.7 = +0.77                                                               L.sub.4        d.sub.4 = 0.31                                                                              1.64   60                                        r.sub.8 = +4.02                                                                              s.sub.4 = 0.12                                                 r.sub.9 = -3.25                                                               L.sub.5 '      d.sub.5 '  = 0.32                                                                           1.81   25                                        r.sub.910 '=-1.01                                                                            s.sub.910 = 0.01                                               r.sub.910 "=-1.01                                                             L.sub.5 "      d.sub.5 " = 0.06                                                                            1.76   27                                        r.sub.10 = +0.42                                                                             s.sub.5 = 0.18                                                 r.sub.11 = +0.68                                                              L.sub.6        d.sub.6 = 0.19                                                                              1.79   47                                        r.sub.12 = -2.56                                                              ______________________________________                                    